1. Field of the Invention
The invention relates to the setting-up of workpieces for machining, such that the workpiece is accurately aligned on a machining axis and is held in such a way as to allow machining of the outer surface thereof in a single operation.
2. Review of the Prior Art
If a workpiece, whose outer surface is to be machined along its axial length, is held in a chuck, it is necessary to machine this surface in two operations. In a first operation, one end of the surface is machined, the workpiece is then removed from the chuck, turned through 180.degree. and the machined surface is inserted in the chuck. Then the remainder of the surface is machined in a second operation. This has the disadvantage that it is a two-operation process, so slowing the production rate and increasing the production cost of workpieces.
In addition, the repositioning of the workpiece will inevitably introduce positioning errors which will, in turn, produce errors in the final surface profile of the workpiece. Thus, the use of a chuck is not practical where a highly accurate profile is required, particularly where, for example, a computer-controlled turning operation is to be performed using a diamond tool, so giving the capability of producing highly accurate complex profiles. This is because the full potential accuracy of the computer control cannot be realised due to chuckpositioning errors.